This section provides background information related to the present disclosure which is not necessarily prior art.
A significant area for reducing energy consumption is outdoor lighting, such as the lighting of large parking lots with pole mounted luminaires. While it is important to provide lighting when people are present, substantial savings could be had if the lights could be switched to a lower level, when people are not present. However, high intensity discharge (HID) lamps typically used in these applications do not respond quickly when turned off and on in an attempt to save energy. Alternatively introducing a means to change light levels (and their associated energy levels) of the HID lamps without allowing the arc inside the lamp to extinguish would enable the lamp to instantaneously respond to the various passive and active control methodologies.
Active control methodologies would include the use of motion sensors to operate the HID lamps at full intensity only when people are present. In contrast, passive control methodologies would leave the lamps operating at full intensity during the times when people are likely to be present, and only operate them at low intensity during times when people are less likely to be present. This type of control, however, requires information about the current time, and it is difficult to retrofit a control with reliable time keeping to a plurality of individual lights, and keep the time for each control accurate and synchronized with the other controls when power to the pole lighting assembly is interrupted by an external switching process. Typically, the lights are only powered during the evening time, and without power the controls cannot maintain the current time.